The present invention relates to a cleaning tape for cleaning a magnetic head installed in magnetic recording-reproducing equipment.
When a magnetic tape is traveled in magnetic recording-reproducing equipment for audio use, video use or computer use, stains tend to adhere to a surface (in contact with the magnetic tape) of a magnetic head (hereinafter sometimes simply referred to as xe2x80x9cheadxe2x80x9d) or tape-traveling systems such as guide rolls. If such stains are left uncleaned, they will cause various problems such that they will interfere with the accurate traveling of the tape or decrease a reproduction output. Thus, the head and the tape-traveling system should be periodically cleaned to avoid such problems and maintain the reliability of the magnetic recording-reproducing equipment.
A cleaning tape used for such a cleaning purpose (herein a dry-type cleaning tape using no organic solvent) comprises a nonmagnetic support having, on one surface thereof, a cleaning layer which contains a magnetic powder, an abrasive, carbon black (an antistatic agent), a lubricant and a binder. To clean the magnetic head and the like, the cleaning tape is traveled with allowing the cleaning layer in contact with the surface of the magnetic head and the like. Thereby, the surface of the head and the like are abraded with the abrasive in the cleaning head. As a result, the stains adhered to the surface of the magnetic head and the like is scraped off and removed. In the cleaning step, the cleaning tape should be traveled while being in contact with the surface of the magnetic head under substantially the same conditions as those under which a magnetic tape travels, so that the surface of the magnetic head is not flawed, or the contact condition between the magnetic head and the magnetic tape (namely, head contact) is not altered. That is, it is necessary for the cleaning tape to reproduce the same contact with the head as the magnetic tape. Such a requirement becomes increasingly strict in these years with the adoption of a MR head, that is, a magnetic head comprising a magnetoresistance effect device) having a high sensitivity. A system having a MR head with a high sensitivity uses a one-reel cassette, which is shown in FIG. 1, as a cleaning tape cassette.
The structure of the one-reel cassette of FIG. 1 will be explained. The one-reel cassette comprises the box-shaped case body 1, which is made by bonding the upper and lower cases 1a and 1b in the cover-shut state, and the cleaning tape 3 which is wound on the single reel 2 installed in the case body 1. The tape-pulling opening 4 opens at one side end of the front wall 6 of the case body 1. The opening 4 is opened and closed with the slidable door 5. To manipulate the cleaning tape 3 with drawing it outside the case from the reel, the tape-drawing equipment 7 is connected with the leading end of the cleaning tape 3. The cassette has the door spring 20 for moving the door 5 to the closed position.
In the meantime, the cleaning tapes described above are produced with a production line of magnetic tapes rather than a production line exclusive for the cleaning tapes mainly from the viewpoint of production costs (see, for example, JP-A-2000-57541). That is, the cleaning tapes are produced with substantially the same materials as those used for the production of the magnetic tapes by substantially the same process as that for the production of the magnetic tapes. Therefore, in some cases, the cleaning tapes are produced with forming a primer layer between the nonmagnetic support and the cleaning layer (which corresponds to the magnetic layer of the magnetic tape), or a back coat layer on the back surface of the nonmagnetic support (the surface opposite to the surface on which the cleaning layer is formed). The major differences of the cleaning tape and the magnetic tape are that the cleaning tape contains the relatively large amount of the abrasive in the cleaning layer to achieve the intended cleaning effect, that the surface of the cleaning layer is made relatively rough by the elimination of a calendering step in the production process or by the change of the conditions of the calendering step, and that the length of the tape of the cleaning tape is shorter than that of the magnetic tape.
Another type of a cleaning tape is known from, for example, JP-A-6-274839 and JP-A-2000-11340. In such a cleaning tape, to avoid the excessive cleaning of the magnetic head, data for monitoring are recording in the surface layer of the cleaning layer, and whether the magnetic head is properly cleaned is judged from the change of the output of the above data which are read with the magnetic head in the course of cleaning. Furthermore, a cleaning tape is known, in which a signal is recorded in a region of the cleaning tape which has bean used, and an unused region of the cleaning tape is used to clean the magnetic head. Such cleaning tapes are used in the one-reel cassette cleaning system described above. With such cleaning tapes, it is preferable that the cleaning layer has specific output characteristics and electromagnetic conversion characteristics so that the cleaning condition or the used regions can be exactly judged from the data read. From such a viewpoint, the cleaning tapes are produced from substantially the same materials as those used for the production of the magnetic tapes.
In these years, in the field of the magnetic recording-reproducing equipment and the magnetic recording media, the recording wavelength has been shortened and the thickness and the length of the tape are reduced and increased to increase the recording density. Thus, the contact condition of the magnetic tape to the magnetic head should be maintained more accurately than ever. Otherwise, a sufficient reproducing output cannot be attained.
In addition, recently, equipment for recording and reproducing magnetic tapes having the MR head described above as the magnetic head is practiced. However, the MR head causes electrostatic breakdown when a material largely charged is in contact with the MR head, while the magnetic field from the tape is disordered with the magnetic field generated with an electric current from the magnetic head to the tape so that noise is generated in the MR head when a material having excessively high conductivity is in contact with the MR head. In either case, the MR head cannot function normally. Therefore, the requirement for the conductivity of the cleaning tape for cleaning the MR head becomes more and more strict. With the stains on the surface of the magnetic head, more strict control is required than with a MIG head (a metal-in-gap type magnetic head).
In spite of the decrease of the recording wavelength and the promotion of the thinning and elongation of the tape as the medium in the field of magnetic recording in these years, the conventional cleaning tape cannot cope with such technical progresses and changes. For example, one problem is the conductivity of the cleaning tape. That is, it is necessary to suppress the charge of the cleaning tape for cleaning the MR head to avoid the electrostatic breakdown caused by the contact, while the conductivity should not be excessively high to avoid the generation of the current caused by the contact of the tape with the magnetic head. However, these points are not taken into consideration with the conventional cleaning tape, which has a specific surface resistivity of 1010 xcexa9/cm2 to 1013 xcexa9/cm2. Therefore, the conventional cleaning tape may cause the electrostatic breakdown caused by the contact with the MR head.
The conventional cleaning tape may unevenly abrade the magnetic head because of the deterioration of the contact of the tape with the head due to the thinning of the tape. That is, the thickness of the cleaning tape and the contact of the tape with the magnetic head have a close relationship. Thus, when the magnetic tape is made thin, the cleaning tape is also made thin so that the cleaning tape attains the same contact with the head as the magnetic tape made thin. However, since the cleaning tape has the larger abrasion property than the magnetic tape, simple thinning of the cleaning tape may lead to the uneven abrasion of the magnetic head because of the deterioration of the contact of the cleaning tape with the head caused by the thinning of the cleaning tape.
One object of the present invention is to provide a cleaning tape which is suitable for cleaning the high sensitivity magnetic head such as the MR head and does not cause performance failure due to the electrostatic breakdown of the magnetic head or the generation of an electric current.
Another object of the present invention is to provide a cleaning head which can achieve good contact with the head and thus avoid the uneven abrasion of the magnetic head.
According to the present invention, the above objects can be achieved by a cleaning tape for a magnetic head system having a magnetoresistance effect head as a reproducing head, comprising a nonmagnetic support, and a cleaning layer containing a magnetic powder and a binder formed on one surface of said support, wherein said cleaning layer has a specific surface resistivity of 3xc3x97103 to 5xc3x97108 xcexa9/cm2 according to JIS C 6240-1970U.